CONTRIBUTIONS ON THE CORN ROOT-APHIS. 117 



had been produced and on November 20 one wingless viviparous 

 female remained alive. The experiment was closed November 20. 



These experiments show that the Erigeron aphis can be transferred 

 to corn or cotton roots and will live on these plants. It seems to take 

 to these plants more readily early in the spring or late in the summer, 

 when a migration from a wild food plant is about to take place. The 

 fact that, when grown on corn, this aphis still retains its distinctive 

 characters, instead of acquiring the characters of Aphis maidi-radicis, 

 goes to show that these two are distinct species. 



Mr. Hyslop and Mr. Kelly carried on experiments of a different 

 nature for the purpose of determining these points. 



Mr. J. A. Hyslop, on July 29, 1908, found specimens of Erigeron 

 canadensis in the grounds of the U. S. Department of Agri- 

 culture at Washington, D. C., badly infested with this aphis. Near 

 these plants he planted corn, watermelon, and cucumber seeds. On 

 September 23 he pulled all of these plants. The Erigeron plants 

 were infested, but no aphides were found on the other plants, even 

 though the roots intermingled in many instances. 



On August 11 Messrs. Kelly and Urbahns, at Wellington, Kans., 

 planted corn, squash, cucumber, and watermelon near an infested 

 Erigeron plant. These plants were watched till October 12, during 

 which time the aphides continued on the Erigeron, but were found 

 at no time on the other plants. 



Mr. Kelly, at Wellington, Kans., on August 26, 1908, planted corn, 

 watermelon, cucumber, squash, and pumpkin seeds near infested 

 plants of Erigeron canadensis. He examined these plants, Septem- 

 ber 29, but found aphides only on the Erigeron, although the roots of 

 the plants often intermingled. 



These experiments show that under natural conditions in the field 

 this aphis will not change from the Erigeron to the corn. What it 

 would do if forced to leave the Erigeron is uncertain, but we have 

 no evidence thus far that it can live for any very long time on the 

 roots of corn. 



While making a trip through the Northwest, in June, 1908, for the 

 purpose of studying the insects affecting cereal and forage crops, Mr. 

 Kelly made a careful study of Aphis maidi-radicis and A. mid- 

 dletoni. At Hastings, Kearney, Columbus, and Fremont, Nebr., and 

 at Missouri Valley and Marshalltown, Iowa, Aphis maidi-radicis 

 was common on the roots of corn ; but although Erigeron canadensis 

 was plentiful, the roots sometimes intermingling with the roots of 

 corn, there were no aphides on the roots of Erigeron. At Bismarck, 

 N. Dak., and Norton and Phillipsburg, Kans., the Erigeron plants 

 were common and had aphides on their roots, but there were no 

 aphides on the roots of corn. 



